A. Field of the Invention
The present invention relates generally to the field of Radio Frequency Identification (hereinafter, “RFID”) systems, and more particularly to a scalable, multi-transceiver RFID reader system having a centralized control and frequency source.
B. Background of the Invention
The ability to track and monitor goods is an important requirement in the proper management of inventories. RFID systems allow a user to track the location of RFID tags and retrieve certain information about the RFID tag. These RFID tags are typically located on a particular item or group of items, which allows for location tracking of the item(s), and may also provide information about the item(s). For example, an RFID tag may contain an expiration date of an associated item and may transmit this information to an RFID reader in response to an interrogation command. One skilled in the art will recognize that RFID tags may provide numerous types and amounts of information about an associated item.
An RFID reader typically queries an RFID tag by transmitting an interrogation command that specifically identifies one or more tags and which also may request certain information. The appropriate RFID tag(s) respond to the interrogation command by transmitting a response with the appropriate information. In a typical passive RFID system, the RFID tag extracts sufficient power from the read field to enable a response to be generated. This read field is usually generated by modulating an interrogation command onto an RF carrier signal and transmitting the resulting RF signal from the reader. This transmitted RF signal creates an RF field, typically of very limited area, in which a tag can extract power, process the command, and subsequently respond to the command. After transmitting a request, the reader may maintain a constant RF carrier signal to generate an RF field that allows the tag to reply.
FIG. 1 generally illustrates an exemplary multi-transceiver RFID system. A centralized reader device 110 is coupled to multiple read zones 120 that interrogate and communicate with RFID tags. Each of the read zones 120 has an associated read field 130 in which communication between a read zone and tag may occur. Tags outside of the read field 130 are usually unable to reliably communicate with the corresponding read zone. One manner in which this read field may be measured is a radius distance 135 in which the field radially extends from the read zone 120.
Accordingly, in a system employing multiple read zones, an approximate location of an RFID tag may be identified based on which read zone is able to communicate with which tag. This communication from the tag is subsequently provided by the read zone to the centralized reader device 110 for processing.
The accuracy of the RFID system depends on a number of factors including the number of read zones, the interrogation power and corresponding size of the read fields, and the quality of components within the system. For example, certain high frequency (hereinafter, “HF”) RFID systems may require RF transmission cabling, multiplexers and other components that are more able to effectively operate within an RF environment. These RF components can be expensive and significantly increase the cost of deploying and maintaining an RFID system. For example, the cost of RF switching components may present a significant deterrent to scaling the number of read zones because multiple RF switches may need to be coupled together to provide sufficient switching capability to address all of the read zones.
One skilled in the art will recognize that the cost of an RFID system may also significantly increase as the number of read zones, and associated RF components, becomes larger. In many instances, the cost of installing and maintaining an RFID system is determinative in whether the system is deployed by a user.